The proliferation of printed data has created a demand for data reduction technologies. Prime among such technologies has been computer graphics and its related field, computer graphics printing. Graphic printing techniques have evolved at a rapid pace and have included trends toward higher information density, full color printing, and higher printing speeds.
Those trends have driven printer technology in a number of areas. One such area is graphic print head technology. Print heads are electronically driven devices that form both characters and shapes as images on a print medium. Print heads form printed shapes by utilizing a variety of technologies including thermal impression, impact, electrographic, laser imaging, and ink jets. Typical print heads are manufactured as fixed or movable arrays of individual printing elements.
FIG. 1 is a schematic drawing of a prior art ink jet printing system 10 that incorporates a print head 12 containing an array of minute circular ink jet orifices 14 each of which ejects a droplet of ink 16 along an ink path 18 toward a print medium 20 to form an image 22. Print medium 20 is advanced in a direction 24 by the rotation of a media feed drum 26. Print head 12 is attached to an ink reservoir 28, which is mounted to a movable carriage 30 that slides on a guide rail 32. Carriage 30 is driven in a reciprocating motion 34 along the length of guide rail 32 by a drive band 36 wrapped around a pair of drive hubs 38. The printing of image 22 is accomplished by the controlled ejection of droplets of ink 16 from ink jet orifices 14 at times coordinated with the position of print head 12 relative to print medium 20.
FIG. 2 illustrates a typical prior art ink jet head assembly 40 such as that manufactured by Sharp, Limited, Nara, Japan. Ink jet head assembly 40 incorporates print head 12 having multiple ink jet orifices 14. Print head 12 is attached to ink reservoir 28 and mounted to carriage 30. One end of ink reservoir 28 is firmly attached to carriage 30 by a mounting screw 41 near a side margin 42 of a base surface 43. The other end of ink reservoir 28 is forced apart from carriage 30 by a jack screw 44 near the other side margin 42 of base surface 43. Turning jack screw 44 alters an azimuthal angle 45, which is defined as the angular displacement between the base surface 43 of ink reservoir 28 and a longitudinal axis 46 of guide rail 32. A change in azimuthal angle 45 changes the slope of an imaginary line 47 connecting the centers of ink jet orifices 14, thereby affecting their vertical spacing.
Droplets of ink 16 deposited on print medium 20 in a single pass of print head 12 undergoing reciprocating motion 34 define what is called a print band 48 having a vertical height 49. Problems associated with the use of jack screw mechanisms include mechanical instability, limited adjustment sensitivity, and interaction between the adjustment of azimuthal angle 45 and vertical height 49 of print band 48.